Spinneret fabrication process

ABSTRACT

A spinneret fabrication process that includes the steps of punching a countersink in the bottom of previously formed counterbores of a spinneret plate, then punching through the countersinks to form capillaries is improved in the countersink and the capillary forming steps by first punching the countersink against an indented head pin anvil and then punching the capillary using a thin dead-soft metal between the spinneret and a back-up plate supported in the immediate area of the countersink by a flat head pin anvil.

Unite States atent [1 1 Anthony et a1.

[ Mar. 4, 1975 3,303,530 2/1967 Cobb, Jr. 76/107 5 X 3,362,265 1/1968 Thompson i 76/107 5 3,668,948 6/1972 Lavinder 76/107 S Primary E.\'aminer-Leonidas Vlachos [57] ABSTRACT A spinneret fabrication process that includes the steps of punching a countersink in the: bottom of previously formed counterbores of a spinneret plate, then punching through the countersinks to tform capillaries is improved in the countersink and the capillary forming steps by first punching the countersink against an indented head pin anvil and then punching the capillary using a thin dead-soft metal between the spinneret and a back-up plate supported in the immediate area of the countersink by a flat head pin anvil.

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SPIN NERET FABRICATION PROCESS BACKGROUND OF THE INVENTION This invention concerns the fabrication of spinnerets for the shaping of textile filaments. More specifically, it concerns the fabrication of spinnerets for spinning filaments with complex nonround cross sections.

Ever increasing percentages of the total production of synthetic textile filaments are of nonround crosssectional shapes, e.g., hexalobal, octalobal, multi-void hollow and similar configurations. The aesthetic properties of yarns and fabrics comprising these complexshaped filaments depend critically on the dimensional uniformity of the spinneret capillaries through which the filaments are spun. The production of complex capillaries consisting of narrow webs and arcs, such as are, for instance, disclosed by Krummeck in US. Pat. No. 3, l 87,607 imposes great stress on the punches used. To reduce the stress, capillary length (i.e., the length of the terminal parallel-sided passage which shapes extruded polymer-melt) has been shortened, but the shorter capillary length has imposed narrower dimensional tolerances for obtaining acceptable filament-to-filament uniformity.

Typical capillary lengths for these complex spinneret orifices are 0.005 inch or less and this dimension must be maintained uniform within extremely close tolerances. Lavinder, in US. Pat. No. 3,668,948 discloses a technique for attaining improved tolerances when punching countersinks and capillaries through the thin metal layer (e.g., 0.010 to 0.020 inch) remaining in spinneret plates after counterbores have been provided. The improvement of Lavinders patent comprises positioning each counterbore over a flat head pin anvil to support the immediate area of each counterbore during respective forming and punching steps. Preferably, the pin anvil is hardened to about Rockwell C 60-62 and a back-up layer of aluminum or steel optionally covered with polyester film is interposed between the spinneret plate and the pin anvil.

Frequently, the punching of complex spinning capillaries involves punching out metal to leave pointed metal projections, i.e., portions of remaining metal where adjacent capillary walls converge to a sharp edge intersection. Such is the case, for example, in punching capillaries which in cross section have rectangular legs meeting at a common center and equiangularly radiating from the common center. As the included angle between adjacent converging capillary walls decreases, the pointed intersections become progressively weaker. Consequently, the tendency for these points both to tear or to be pushed down by the punch to reduced irregular capillary lengths increases. Moreover, the punches themselves become more fragile. It is observed that when the included angle of convergence of adjacent capillary walls is less than or about 72, even the improved process of the aforesaid US. Pat. No. 3,668,948 is inadequate for maintaining the necessary tolerances in complex spinning capillaries.

SUMMARY OF THE INVENTION In a spinneret fabrication process that includes the steps of forming a plurality of counterbores in one side of a spinneret plate, punching a countersink in the bottom ofeach counterbore to a preselected depth of penetration; and punching through the countersink to form a capillary, the improvement comprising: positioning each ofsaid counterbores over a pin anvil having a head with a central indentation therein; and supporting the area surrounding said capillary with said anvil while extruding metal from the other side of the spinneret plate into said indentation during the punching of said countersink. The process also includes the steps of removing the metal extruded into said indentation during said countersink forming step; supporting the other side of the spinneret plate with a layer of dead-soft metal having a thickness of from about 0.001 to about 0.003 inch and metal plate; replacing the indented head anvil with a flat head pin anvil; then positioning each countersink over the flat head pin anvil; and supporting the immediate area of each countersink with said flat head anvil during the punching of the capillary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation in cross section of countersink formation according to this invention.

FIG. 2 is a schematic representation in cross section of capillary punching according to this invention.

FIG. 3 is a greatly enlarged view in cross section of a typical spinning orifice made according to this invention.

FIG. 4 shows in further enlarged view the shape ofa typical capillary opening as seen at 44 of FIG. 3.

FIG. 5 is an enlarged side-view of a countersinkforming tool typically employed.

FIG. 6 is a view taken at 6-6 of FIG. 5 of the countersink-forming tool.

FIG. 7 is an enlarged side view of a capillary punch typically employed.

FIG. 8 is an end view taken at 8-8 of FIG. 7 of the capillary punch.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The present invention enables forming a countersink and then punching a capillary in the thin web of metal (i.e., 0.010 to 0.020 inch) remaining at the flat bottom ofa counterbore preformed in a spinneret plate. While not at all so limited, it is particularly effective in generating nonround capillaries and more especially those in which adjacent capillary walls converge to a sharp edge with an included angle of less than or about 72. The invention is discussed below as it relates to the form ation of capillaries with an octalobal cross section.

By octalobal cross section is meant, the shape of capillary opening 45 as shown in FIG. 4. Four rectangular openings 40 intersect at and are symmetrically spaced about a common center 42. Dimension D is the overall diameter of capillary opening 45 and W is the width of each rectangular portion 40. Adjacent walls everywhere converge to sharp edges having included angle (a) of 45.

FIG. 1 shows spinneret plate 10 mounted for forming a countersink. Spinneret plate 10 is secured with bolts 14 to ring 16 which surrounds an open area bounded at the top by the face of spinneret plate 10 and at the bottom by base plate 12 fixed to the body of a punch press. Previously formed, flat-bottomed counterbore 18 is shown in position under countersink-forming tool 20 ready for forming a countersink. Axially aligned directly under counterbore 18 is a pin anvil 22 having a central indentation 24 in its head. Anvil 22 is preferably hardened to at least Rockwell C 60-62. Indentation 24 is a cylindrical flat-bottomed axially centered hole having a diameter of two to four times dimension D (FIG. 4) and a depth approximately one-half the depth of penetration of tool 20 into the bottom of counterbore 18. Pin anvil 22 supports spinneret plate to prevent bowing. Indentation 24 provides space to receive metal extruded by countersink forming, but its restricted depth causes extruded metal to spread laterally, thus, exerting back pressure in the immediate punching area and preventing local distortion. Position 26 is shown with countersink 28 already formed, the nub 29 of extruded metal being flat-bottomed. Before capillary punching, nubs 29 are removed by customary finishing procedures.

FIG. 2 represents the process of punching capillaries in holes already provided with countersinks as described above in connection with FIG. 1. With respect to base plate 12, ring 16, spinneret plate 10 and bolts 14, the arrangement is just as in FIG. 1. Counterbore 18 with preformed countersink 28 is positioned for punching with capillary tool 30. Axially aligned underneath is a flat head pin anvil 32 as disclosed by Lavinder in U.S. Pat. No. 3,668,948. Back-up plate 34 of hardened metal is positioned against the top of pin anvil 32, and a thin layer 36 of dead soft metal is interposed between plate 34 and spinneret plate 10. Punch 30 is pushed completely through the remaining thickness (usually 0.005 inch or less) of metal in spinneret plate 10. Position 26 is shown already punched. The tiny extruded nub 38 of metal displaces immediately adjacent portions of dead-soft layer 36 thus generating considerable back pressure beneath the complex portions contacting the punch in its passage downward for capillary punching. Especially, the sharp-pointed edges of the capillary tend to be displaced downward. It is found that a critical combination of hardness for backup plate 34 and thickness of dead-soft metal 36 eliminates or at least reduces to acceptable levels the distortion of the spinneret capillary.

Optimum punching uniformity results when plate 34 has a hardness of Rockwell B 65 to 80, preferably being aluminum sheet about 0.040 to 0.080 inch thick. Dead-. soft layer 36 optimally has a thickness of 0.001 to 0.003 inch and is composed of unhardened metal (e.g., aluminum or brass). Particularly preferred for the combination of layers 34 and 36 is a product known as clad aluminum, the base being of hardness Rockwell B 67-72 and having a coating of dead-soft aluminum about 00018 to 0.0022 inch thick. The base with cladding on both surfaces is equally suitable.

A typical spinning orifice fabricated using the process of this invention is shown in cross section in FIG. 3. It is a spinning orifice disclosed by Cobb in U.S. Pat. No. 3,303,530 in which the walls of the odd cross section spinning capillary 50 are substantially normal to discharge face 52 and are of equal height at all points along the periphery. Countersink 48 is a first divergent section" with uninterrupted planar surfaces each diverging from one of the capillary walls. Counterbore 18 is typically 0.070 inch in diameter. The tool providing flat bottom 44 usually provides a taper 46 with about a 90 included angle. Countersink 48, in the particular case of this description, is punched to about a 0.010 inch depth, the punching operation drawing down flat bottom 44 outside the punched area so that no sharp edges remain at the entrance to the countersink. Octalobal spinning capillary 50 is 0.005 inch or less in depth.

The Working end of a suitable countersink-forming tool 20 is shown in FIGS. 5 and 6. An appropriately sized cylindrical rod 54 of tool stock is tapered conically with an included angle of about 50 to a terminal circular diameter equal to or slightly exceeding dimension D (FIG. 4). Flat area 56 is the only portion of original flat end 58 not removed in forming the tool and it has the shape and size of the cross section of the ultimately produced capillary. A V-trough 66 is formed between each pair of adjacent legs of Area 56, the straight line 60 of deepest penetration extending from point 62 (FIG. 5) to the junction of legs of Area 56 at end 58. Each angled flat wall 64 of V-troughs 66 provides a taper to one side wall of a leg of the ultimate spinning capillary. Each flat area 68 likewise provides a taper to the end wall of the ultimate spinning capillary. Countersink-forming tool 20 is, of course, hardened before use in forming countersinks.

FIGS. 7 and 8 similarly show the working end of capillary punch 30. It has eight parallel-walled symmetrically spaced legs 70 intersecting at common center 72. Dimension D (FIG. 4) is 0.032 inch in the embodiment described, and dimension W (FIG. 4) is 0.0035 inch.

The leading edges 74 of legs 70 are preferably slightly chamfered as shown.

Octalobal capillaries are formed in a spinneret plate with counterbores already provided to leave 0.015 inch of metal between the flat bottom of each counterbore and the face of the spinneret. The countersink-forming tool of FIGS. 5 and 6 is used in the process of FIG. 1, penetration of the tool being to a depth of 0.010 inch and indentation 24 of pin anvil 22 being 0.0625 inch in diameter and 0.0045 inch deep. Outside diameter of the head of pin anvil 22 is 0.156 inch. Capillary punching uses the tool of FIGS. 7 and 8 in the process of FIG. 2. Back-up plate 34 (FIG. 2) is 0.060 inch thick aluminum of hardness Rockwell B 67-72. Various dead-soft metal layers 36 are employed, as listed in Table I. It is seen that thicknesses of dead-soft metal from 0.001 to 0.003 inch provide improved retention of capillary depth, measured at the pointed intersections of the capillary legs, as compared either to the use of no deadsoft layer 36 or thicker layers. The preferred clad aluminum has a dead-soft aluminum layer 0.002 t 0.0002 inch thick.

TABLE I COMPARISON OF DEAD-SOFT METAL LAYERS Capillary Depth In all cases shown in Table I where a dead-soft layer 36 is employed, more than 500 capillaries are formed before each punch breaks, i.e., punch breakage is low. For the single case not utilizing a dead-soft layer 36,

less than 100 holes can be punched before each punch breaks.

While the present invention has been illustrated for the fabrication of octalobal capillaries, it is equally effective in forming odd cross sections ranging from pentalobal to decilobal, or higher. The invention is also equally effective in forming capillaries of which the legs are not all of the same cross-section and/or are not equiangularly spaced. It has heretofore been impossible to fabricate multilobal capillaries with acceptable retention of capillary depth at the pointed intersections of capillary legs. Not only does the present invention improve the maintenance and uniformity of critical capillary dimensions, but also it greatly reduces the failure-rate of punches used to form complex capillaries.

What is claimed is:

1. In a spinneret fabrication process that includes the steps of forming a plurality of counterbores in one side of a spinneret plate, punching a countersink in the bottom of each counterbore to a preselected depth of penetration; and punching through the countersink to form a capillary, the improvement comprising: positioning each of said counterbores over a pin anvil having a head with a central indentation therein; supporting the area surrounding said capillary with said anvil while extruding metal from the other side of the spinneret plate into said indentation during the punching of said countersink; removing the metal extruded into said indentation during said countersink forming step; supporting the other side of the spinneret plate with a layer of dead-soft metal having a thickness; of from about 0.001 to about 0.003 inch and metal plate; replacing the indented head anvil with a flat head. pin anvil; then positioning each countersink over the flat head pin anvil; and supporting the immediate area of each countersink with said flat head anvil during the punching of the capillary.

2. The process as defined in claim 1, said indentation being a flat bottomed cylindricalhole having a depth of about one-half said preselected depth of penetration and having a diameter of from about two to four times the diameter of the capillary.

3. The process as defined in claim 1, said dead-soft metal being aluminum, said metal plate having a hardness of Rockwell B -80.

4. The process as defined in claim 1, said dead-soft 

1. In a spinneret fabrication process that includes the steps of forming a plurality of counterbores in one side of a spinneret plate, punching a countersink in the bottom of each counterbore to a preselected depth of penetration; and punching through the countersink to form a capillary, the improvement comprising: positioning each of said counterbores oveR a pin anvil having a head with a central indentation therein; supporting the area surrounding said capillary with said anvil while extruding metal from the other side of the spinneret plate into said indentation during the punching of said countersink; removing the metal extruded into said indentation during said countersink forming step; supporting the other side of the spinneret plate with a layer of dead-soft metal having a thickness of from about 0.001 to about 0.003 inch and metal plate; replacing the indented head anvil with a flat head pin anvil; then positioning each countersink over the flat head pin anvil; and supporting the immediate area of each countersink with said flat head anvil during the punching of the capillary.
 2. The process as defined in claim 1, said indentation being a flat bottomed cylindrical hole having a depth of about one-half said preselected depth of penetration and having a diameter of from about two to four times the diameter of the capillary.
 3. The process as defined in claim 1, said dead-soft metal being aluminum, said metal plate having a hardness of Rockwell B 65-80.
 4. The process as defined in claim 1, said dead-soft metal being brass. 